1. Field of the Invention
This invention relates in general to circuit arrangements for calculating the quantity of message signals supplied to an ATM switching system during virtual connections which utilizes a plurality of counters which correspond in number to the number of virtual connections and wherein each counter has an individual memory area.
2. Description of the Prior Art
So as to avoid overload in the transmission of cells in broadband switching systems, it has been proposed in the article International Zurich Seminar On Digital Communications of March 1986 entitled "New Directions In Communications A3.1 Through A3.8" by J. B. Turner to allocate a forward-backward counter in a switching node to every subscriber equipment which is connected and the forward-backward counter counts the cells transmitted by the respective subscriber equipment and lowers the momentary counter reading corresponding to the transmission rate defined by respective subscriber equipment at specified times. When the momentary counter exceeds a value prescribed by the respective subscriber equipment, then the switching node recognizes an overload ("leaky bucket" method).
An additional circuit arrangement for avoiding overload in a broadband switching system is described in German published application No. 37 32 937 of which U.S. Pat. No. 5,007,048 is the U.S. equivalent. Instead of a forward-backward counter, two forward counters in this circuit arrangement are allocated in a switching node to every subscriber equipment which is connected and a first counter counts the cells sent by the respective subscriber equipment and the other counter calculates the connection time during the existing call. The two counters are connected to a means which based on the relationship between the counter readings checks the observation of the maximum bit rate defined by the respective subscriber equipment A call charge acquisition is also provided on the basis of the counter readings.